A variety of different applications use sensor systems to detect the movement of an underlying object. Sensors employing microelectromechanical systems (MEMS) devices are increasingly used in such applications due to their relatively small size and their capability to detect relatively small changes in the measured item. MEMS inertial sensor devices, e.g., accelerometers or gyroscopes, typically employ a movable, inertial mass formed with one or more fixed, non-moving structures. For example, in a MEMS accelerometer, the inertial mass may be suspended in a plane above a substrate and movable with respect to the substrate. The movable structure and the fixed structures form a capacitor having a capacitance that changes when the movable structure moves relative to the fixed structures in response to applied forces, such as along a predetermined axis of the device, e.g., x-, y- and z-axes.
Currently, inertial sensors may be used for monitoring the interaction of users with electronic devices, such as gaming devices, cell phones, personal digital assistants, etc. The inertial sensors in the devices may sense a movement above a particular threshold or a change in orientation. The sensors typically cooperate with a central computer or microprocessor that both coordinates their function and responds to specific types of detected movement. Upon detection of a specific type of movement, the sensors may transmit motion data to the central computer, which causes systems within the device to respond in a specified manner. For example, if the sensor(s) detect a tap by the user (e.g., similar to a mouse click), the device's microprocessor may initiate a response, such as turn on the device. Similarly, if the sensor(s) detect a rotation, e.g., the user turns the display 180 degrees, the device's microprocessor may change the orientation of the image display.
At present, there is no integrated, automated method for an inertial sensor to indicate different conditions of the device, e.g., its active or inactive state, without interaction with the microprocessor. These functions usually exist separately from the inertial sensor. Typically, the microprocessor or controller periodically (or continuously) monitors the acceleration data from the inertial sensor to determine the state of the device.